JP2008006689A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of easily and with a simple constitution preventing banding from being generated. <P>SOLUTION: In the image forming apparatus, dots formed on a recording paper are formed alternately on straight lines on a raster (line) formed in a perpendicular direction to the conveying direction of a recording paper as shown in Fig.2(a), and then, dots alternately skipped on the preceding raster are formed at the raster position moved to the conveying direction by a half of the interval of an ordinary line. Fig.2(b) shows that conveying skip is generated when the dots are zigzag-formed. Two parallel solid lines shown in the perpendicular direction to the conveying direction are positions generating white stripes, and as the dots are arranged in a zigzag-like shape, it is found that the blank does not form a straight-like shape. Therefore, by making a dot arrangement like this, banding can be prevented from being generated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that can prevent banding that occurs when the conveyance of a recording medium is not uniform.

  FIG. 10 is a side view showing a printer unit 1a of a color ink jet printer as a conventional image forming apparatus. The ink jet printer uses the printer unit 1a to print the read data on recording paper. The printer unit 1a includes a conveyance roller 101, a pinch roller 102, a paper discharge roller 103, spurs 104 and 105, a conveyance motor (not shown) that drives these rollers 101 and 103, and the presence or absence of recording paper. A paper sensor 106 for detecting, a platen 108, and an inkjet head 109 are provided. In FIG. 10, an arrow Z indicates the conveyance direction of the recording paper introduced into the apparatus.

  The inkjet head 109 is mounted on a carriage (see FIG. 1), which will be described later, and reciprocates in a direction perpendicular to the recording paper conveyance direction (perpendicular to the paper surface in FIG. 10). The inkjet head 109 includes cyan and magenta. Ink, yellow, black, etc. are supplied from an ink cartridge (not shown) that stores each ink, and the supplied ink is ejected from one of a number of nozzles formed on the inkjet head 109 onto a recording sheet. The inkjet head 109 is formed with a plurality of nozzles for each color at equal intervals in a direction substantially parallel to the transport direction.

  A platen 108 is provided on the opposite surface of the inkjet head 109 on the back side (opposite side of the printing surface) of the recording paper to be conveyed. The recording paper to be conveyed is introduced into the gap between the platen 108 and the inkjet head 109.

  In the printer unit 1 a, the transport roller 101 is provided on the upstream side in the paper transport direction from the inkjet head 109. The transport roller 101 sandwiches the recording paper by a pinch roller 102 provided opposite to the transport roller 101 and feeds the recording paper sandwiched by the rotation of the roller to execute the transport. The recording paper that has passed through the transport roller 101 is introduced directly under the inkjet head 109.

  A paper discharge roller 103 is provided on the downstream side of the transport roller 101 and downstream of the position where the inkjet head 109 is disposed. The paper discharge roller 103 is also a roller that performs conveyance while sandwiching the recording paper with a spur 104 provided opposite to the paper discharge roller 103. The spur 104 is a rotating body formed so that the surface thereof is uneven, and is provided above the paper discharge roller 103 and is in contact with the printing surface of the printed recording paper. Since the ink on the printing surface immediately after printing is undried, if a roller with a large contact area comes into contact with the printing surface, bleeding, kinking, ink transfer to the roller, and the like are likely to occur, and the printing quality is liable to deteriorate. Therefore, the roller that contacts the print surface of the printed recording paper is spurred to reduce the contact area with the print surface and prevent the print quality from deteriorating.

  The transport roller 101 and the paper discharge roller 103 are driven by a transport motor (not shown) that is a recording paper transport drive source. Thus, the transport roller 101 and the paper discharge roller 103 are rotated in the transport direction of the recording paper, and the sandwiched recording paper is sent out and transported by the rollers 101 and 103, the roller 102 and the spur 104 facing each other. To do.

  Therefore, when the recording paper is sandwiched between the conveyance roller 101 and the pinch roller 102, that is, until the trailing edge of the recording paper passes the nip point between the conveyance roller 101 and the pinch roller 102, the recording paper Is conveyed by the conveyance roller 101.

  On the other hand, after the trailing edge of the recording sheet passes through the nip point between the conveying roller 101 and the pinch roller 102, the recording sheet is conveyed by the rotation of the discharge roller 103.

  When the recording paper is nipped and conveyed by the conveyance roller 101 and the pinch roller 102, the paper feeding accuracy is maintained, but the conveyance of the recording paper proceeds and the recording paper is transferred from the conveyance roller 101 and the pinch roller 102. Is released, the end of the recording paper is released, the recording paper is repelled, the paper feeding accuracy becomes unstable, and banding occurs in the formed image.

Japanese Patent Application Laid-Open No. 11-207945 (Patent Document 1) and Japanese Patent Application Laid-Open No. 11-291506 (Patent Document 2) describe that in a region where banding occurs, resolution is increased and banding is suppressed. JP-A-2005-138501 (Patent Document 3) describes a method for reducing the conveyance amount of a recording medium in order to prevent banding.
Japanese Patent Laid-Open No. 11-207945 JP 11-291506 A JP 2005-138501 A

  However, in the inventions described in Patent Documents 1, 2, and 3, banding can be somewhat prevented, but there is a problem that banding may be visually recognized.

  FIG. 11 is a diagram schematically illustrating how banding occurs, and each circle represents a dot formed of ink. FIG. 11A shows a case where printing is performed in a state where the recording paper is nipped and conveyed by the conveying roller 101 and the pinch roller 102, and dots are regularly arranged in a grid pattern. In the normal arrangement in FIG. 11, a raster is formed by dots arranged in a line in a direction intersecting (orthogonal) with the recording paper conveyance direction (Z direction shown in the figure), and the rasters are sequentially arranged in the conveyance direction. That is.

  FIG. 11B shows a case in which the printing is performed in the normal arrangement, and the conveyance is not uniform, but is performed for a moment. The two parallel lines are perpendicular to the conveyance direction. As indicated by the solid line, a linear blank is generated. Due to this phenomenon, white stripes are generated in a direction perpendicular to the transport direction.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can easily prevent banding with a simple configuration.

  In order to achieve this object, an image forming apparatus according to claim 1 of the present invention forms a raster composed of a plurality of dots at a predetermined interval in a direction intersecting a conveyance direction for conveying a recording medium. A recording means for performing recording, a first conveying member disposed upstream of the recording position of the recording medium in the conveying direction of the recording medium, and a conveying direction with the recording means sandwiched between the first conveying member A second conveying member disposed on the downstream side, driving the first conveying member and the second conveying member to convey the recording medium from the upstream side to the downstream side, and A region where recording is performed by the recording unit while transporting the recording medium by the first transport member is defined as a first region, and a region where recording is performed by the recording unit while transporting only by the second transport unit is defined as a second region. age, A first intermediate region when a predetermined region not adjacent to the second region is defined as a first intermediate region and a region sandwiched between the first intermediate region and the second region is defined as a second intermediate region. In the first area recorded earlier, the resolution in the conveyance direction of recording by the recording means is the first resolution, and in the second intermediate area, the resolution in the conveyance direction is the second resolution higher than the first resolution. The first intermediate area includes control means for gradually increasing the resolution from the first resolution to the second resolution as the resolution in the transport direction approaches the second intermediate area. In the present application, a dot row in a row (perpendicular to the direction in which the recording medium is conveyed) formed on the recording medium is particularly referred to as a raster.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the control unit includes a section in which recording is performed at a first resolution in the transport direction of the recording medium in the first intermediate region. The resolution is gradually increased by changing the ratio of the recording interval with the second resolution.

  The image forming apparatus according to claim 3, wherein the control unit includes the second intermediate area and a section in the first intermediate area where recording is performed at the second resolution. Then, one raster is divided into a plurality of areas, and the plurality of divided areas are arranged such that adjacent areas are shifted in the respective transport directions.

  The image forming apparatus according to claim 4 includes a recording unit that performs recording by forming a raster composed of a plurality of dots at a predetermined interval in a direction intersecting a conveyance direction in which the recording medium is conveyed, and the recording unit. A first transport member disposed upstream of the recording position in the transport direction of the recording medium, and a second transport member disposed downstream of the first transport member with the recording means interposed therebetween And conveying means for driving the first conveying member and the second conveying member to convey the recording medium from the upstream side to the downstream side, and conveying the recording medium by the first conveying member. When the area to be performed is the first area, the area to be transported only by the second transport means is the second area, and among the first area, a predetermined area adjacent to the second area is an intermediate area, Recorded before the middle area In the first area, the resolution in the conveyance direction of the recording by the recording means is the first resolution, and in the intermediate area, the resolution in the conveyance direction is the second resolution that is higher than the first resolution. And a control unit that divides the raster into a plurality of regions and arranges the divided regions so that adjacent regions are shifted in the respective transport directions.

  The image forming apparatus according to claim 5, wherein the control unit sets the resolution in the transport direction in the second region to a resolution lower than the second resolution. To do.

  According to a sixth aspect of the present invention, in the image forming apparatus according to the fifth aspect, when a predetermined area adjacent to the first area in the second area is set as a third intermediate area, a third intermediate area is provided. The area includes control means for gradually decreasing the resolution in the transport direction from the second resolution to the first resolution as the distance from the first area increases.

  The image forming apparatus according to claim 7, wherein the control unit performs recording at the first resolution in the transport direction of the recording medium in the third intermediate area. Then, the resolution is gradually lowered by gradually changing the ratio of the recording interval with the second resolution.

  The image forming apparatus according to claim 8, wherein in the third intermediate area, the control unit divides one raster into a plurality of areas, and the divided plurality of areas. Are arranged such that adjacent areas are displaced in the respective transport directions.

  According to the image forming apparatus of the first aspect, the area where recording is performed by the recording unit while the recording medium is transported by the first transport member is the first region, and the recording unit is transported only by the second transport unit. The recording area is a second area, and a predetermined area not adjacent to the second area is a first intermediate area, and an area sandwiched between the first and second areas is a second area. In the case of the intermediate area, in the first area recorded before the first intermediate area, the resolution in the recording conveyance direction by the recording means is the first resolution, and in the second intermediate area, the resolution in the conveyance direction is the first resolution. Control means for gradually increasing the resolution from the first resolution to the second resolution as the resolution in the transport direction approaches the second intermediate area in the first intermediate area. Because the second middle territory When an image is formed on the screen, banding can be prevented even if the conveyance is disturbed, and the resolution is gradually increased, so that the change in the image due to the change in resolution can be moderated. There is an effect that a high-quality image can be formed.

  According to the image forming apparatus of the second aspect, in addition to the effect produced by the image forming apparatus of the first aspect, the control unit performs recording at the first resolution in the transport direction of the recording medium in the first intermediate area. Since the resolution is gradually increased by changing the ratio of the section to be recorded and the section to be recorded by the second resolution, the resolution can be set only by switching between the first resolution section and the second resolution section. There is an effect that control is easy.

  According to the image forming apparatus of the third aspect, in addition to the effect produced by the image forming apparatus according to the second aspect, the control unit performs recording at the second resolution in the second intermediate area and the first intermediate area. In the section, one raster is divided into a plurality of areas, and the divided areas are arranged so that the adjacent areas are shifted in the respective transport directions. It is not formed, and banding is less conspicuous than when the resolution is simply increased. Therefore, there is an effect that a higher quality image can be formed.

  According to the image forming apparatus of the present invention, the area where the recording medium is conveyed by the first conveying member is the first area, the area where only the second conveying means is conveyed is the second area, and the first area is Of these, when a predetermined area adjacent to the second area is an intermediate area, in the first area recorded before the intermediate area, the resolution in the recording conveyance direction by the recording means is the first resolution, and the intermediate area In the area, the resolution in the transport direction is set to the second resolution that is higher than the first resolution, one raster is divided into a plurality of areas, and the divided areas are transported by adjacent areas. Since the control means is arranged so as to be displaced in the direction, the skipped dots are not formed in a straight line by the shifted dots, and the banding is not conspicuous as compared with the case where the resolution is simply increased. Therefore, there is an effect that banding can be prevented and a high-quality image can be formed by a simple configuration in which some dots are shifted.

  According to the image forming apparatus of the fifth aspect, in addition to the effect produced by the image forming apparatus according to any one of the first to fourth aspects, the control unit may change the resolution in the transport direction in the second area from the second resolution. Since a low resolution is set, in a region where banding does not occur, the resolution can be lowered, the image quality can be maintained, and the image forming speed can be increased.

  According to the image forming apparatus of the sixth aspect, in addition to the effect produced by the image forming apparatus of the fifth aspect, when a predetermined area adjacent to the first area is set as the third intermediate area in the second area. The third intermediate area includes control means for gradually lowering the resolution in the transport direction from the second resolution to the first resolution as the distance from the first area increases, so that the image change due to the change in resolution is moderated. And high-quality images can be formed.

  According to the image forming apparatus of the seventh aspect, in addition to the effect produced by the image forming apparatus according to the sixth aspect, the control means performs recording at the first resolution in the transport direction of the recording medium in the third intermediate region. Since the resolution is gradually lowered by gradually changing the ratio between the section to be performed and the section to be recorded with the second resolution, the resolution can be simply switched between the first resolution section and the second resolution section. Can be set, and control is easy.

  According to the image forming apparatus of the eighth aspect, in addition to the effect produced by the image forming apparatus according to the seventh aspect, the control unit divides one raster into a plurality of areas in the third intermediate area and divides the raster. Since the plurality of areas are arranged so that the adjacent areas are shifted in the respective transport directions, the resolution gradually changes continuously with the second intermediate area which is arranged with the high resolution and the adjacent dot positions shifted. An image can be formed.

  Hereinafter, a color inkjet printer 1 according to a first preferred embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing an outline of an electric circuit configuration of the color inkjet printer 1. The mechanism of the printer unit 1a, which is the main part that performs printing, is the same as that shown in FIG.

  The control device for controlling the color ink jet printer 1 includes a main body side control board 12 and a carriage board 13. The main body side control board 12 includes a one-chip microcomputer (CPU) 32, ROM 33 that stores various control programs executed by CPU 32 and fixed value data, RAM 34 that is a memory for temporarily storing various data and the like, flash memory 35, image memory 37, G / A (Gate array) 36 and the like are mounted.

  The CPU 32, which is an arithmetic unit, generates a print timing signal and a reset signal according to a control program stored in advance in the ROM 33, and transfers each signal to a gate array 36 described later. The CPU 32 also has a CR motor drive circuit for driving an operation panel 45 for a user to issue a print instruction and the like, and a carriage motor (CR motor) 16 for operating a carriage 64 on which the above-described inkjet head 109 is mounted. 39, an LF motor drive circuit 41 for operating a conveyance motor (LF motor) 40 for driving the conveyance roller 101, a paper sensor 106, a linear encoder 43, and a rotary encoder 46 are connected. Controlled by the CPU 32.

  The paper sensor 106 is a sensor that detects the presence or absence of recording paper. The paper sensor 106 is arranged on the upstream side of the conveyance roller 101, and a lever 106a (see FIG. 10) that rotates when contacting the recording paper, and its detector. And a photo interrupter 106b (see FIG. 10) which is a sensor unit for detecting the rotation of the lens. The linear encoder 43 detects the movement amount of the carriage 64, and the reciprocation of the carriage 64 is controlled by detecting the encoder amount of the linear encoder 43 by a photo interrupter (not shown). The rotary encoder 46 detects the rotation amount of the transport roller 101, and the transport roller 101 is controlled by detecting the encoder amount of the rotary encoder 46 with a photo interrupter (not shown). In other words, the actual transport position of the recording paper transported by the transport roller 101 by the rotary encoder 46 can be detected with a predetermined accuracy.

  The ROM 33 stores a print control program 33a for executing a print process, a dot distribution process program 33b for performing a dot position arrangement process for suppressing the occurrence of banding, and the like. In the flash memory 35, correction values for accurately transporting the recording paper and accurately scanning the head are obtained and stored by a test before product shipment. The CPU 32, the ROM 33, the RAM 34, the flash memory 35, and the G / A 36 are connected via a bus line 47.

  Based on the timing signal transferred from the CPU 32 and the image data stored in the image memory 37, the G / A 36 records recording data (driving signal) for recording the image data on recording paper, and the recording A transfer clock that is synchronized with data, a latch signal, a parameter signal for generating a basic drive waveform signal, and a discharge timing signal that is output at a constant cycle are output, and each of these signals is mounted with a head driver. Transfer to the carriage substrate 13.

  The G / A 36 also stores in the image memory 37 image data transferred from an external device such as a computer via an interface (I / F) 44 such as a USB. The G / A 36 generates a data reception interrupt signal based on the data transferred from the computer or the like via the I / F 44 and transfers the signal to the CPU 32. Each signal communicated between the G / A 36 and the carriage substrate 13 is transferred via a harness cable that connects the two.

  The carriage substrate 13 is a substrate for driving the inkjet head 109 by a mounted head driver (drive circuit). The inkjet head 109 and the head driver are connected by a flexible wiring board 19 in which a copper foil wiring pattern is formed on a polyimide film having a thickness of 50 to 150 μm. This head driver is controlled via the G / A 36 mounted on the main body side control board 12 and applies a drive pulse having a waveform suitable for the recording mode to the piezoelectric actuator constituting the inkjet head 109. As a result, a predetermined amount of ink is ejected from the inkjet head 109.

  Next, the arrangement of dots formed on a recording sheet by the image forming apparatus according to the present invention will be described with reference to FIG. FIG. 2 is a schematic diagram showing the arrangement of dots formed on the recording paper. The arrangement of dots in a region where an image is formed with a higher resolution than that in a region where an image is formed with a normal resolution is shown. Similarly to the diagram showing the conventional dot arrangement shown in FIG. 11, each circle indicates a dot formed by ink, and the conveyance direction of the recording paper is indicated by an arrow Z.

  As shown in FIG. 2A, the dots formed on the recording paper by the image forming apparatus according to the present invention are arranged every other column in a row (raster) formed in a direction perpendicular to the recording paper conveyance direction. Are formed in the next raster line, and in the line moved in the transport direction by half the normal line interval, a dot is formed in the skipped column of the previous raster line. In other words, every other row of dots is arranged at a position shifted in the transport direction from the dot position of the adjacent row. FIG. 2A shows a case where printing is performed in a state where the recording paper is normally conveyed, that is, in a state where the recording paper is nipped and conveyed by the conveying roller 101 and the pinch roller 102. Dots are arranged in a staggered pattern.

  FIG. 2B shows a case where the dots are formed in a zigzag pattern and the conveyance is not uniform and is carried large for a moment (when conveyance feed skip occurs). What is indicated by two parallel solid lines in the direction perpendicular to the transport direction is the position of the white streaks shown in FIG. 11B. However, since the dots are arranged in a staggered pattern, the blank does not become a straight line. I understand that. Therefore, with such a dot arrangement, banding can be prevented from occurring.

  As can be seen from these figures, since the dots formed by the image forming apparatus according to the present invention are in a so-called staggered arrangement, as shown in FIG. Since the portion where the paper base is exposed is not formed in a straight line but is formed in a discrete manner, it can be made inconspicuous.

  In the example shown in FIG. 2, it is assumed that every other adjacent dot is displaced in the transport direction. However, every other two dots may be used. In short, one raster is divided into a plurality of regions. The plurality of divided areas are arranged so as to be shifted in the respective transport directions. This can prevent banding from occurring.

  Next, a method for distributing dots formed by the interlace method will be described with reference to FIGS. 3 and 4 show a region where dots are formed with a print resolution of 2400 dpi and a region where dots are formed with a resolution of 4800 dpi corresponding to the progress of the raster. Dots are formed by the interlace method in the direction in which the raster number sequentially increases from the raster 1 shown in FIG. The raster 65, which is the final line shown in FIG. 3, is continuous with the leading raster 67 shown in FIG. Here, the raster number is a line number given from the upper end to the lower end of the raster recording paper, which is a row of dots formed by the head moving in the main scanning direction. In this figure, the description of the top portion of the recording paper is omitted, and the raster is shown as raster 1 from the middle raster.

  Further, the pass number (pass No) described above the raster 1 is the order in which the recording paper is transported, and when dots are formed by the pass at the intersection of the pass number and the line, In the case where no dot is formed, a line formed by pass order with a small dot is shown.

  For example, in FIG. 3, in pass 5, a raster 15 indicated by a black circle 5-1, a raster 23 indicated by a black circle 5-2, a raster 31 indicated by a black circle 5-3, a raster 39 indicated by a black circle 5-4, It is shown that 7 rasters, that is, a raster 47 indicated by a black circle 5-5, a raster 55 indicated by a black circle 5-6, and a raster 63 indicated by a black circle 5-7 are formed at a time. Similarly, in pass 6, rasters 29, 37, 45, 53, 61, and 69 (see FIG. 4) are formed.

  Also, as shown by the downward arrow, when one pass is completed, the recording paper is conveyed in the opposite direction to the arrow for 7 rasters. In this way, the recording paper is sequentially conveyed to form each dot.

  Note that only rasters with odd numbers are formed in the 2400 dpi resolution region. The right side of FIGS. 3 and 4 shows the arrangement of dots formed on the recording paper corresponding to the raster.

  As shown in FIG. 4, between rasters 113 to 132, the resolution is 4800 dpi and the dot arrangement is a staggered arrangement. Since the carry feed skip occurs during printing of this section, only in this section, the resolution is increased and the dot arrangement is changed. As described above, the occurrence of banding in an image to be formed can be suppressed even when the conveyance feed skip occurs due to the staggered arrangement.

  There are 10 to 17 passes for printing in this staggered area. In this pass, the carry amount is half that of 2400 dpi, the resolution is 4800 dpi, even-numbered rasters are formed in even-numbered passes, and odd-numbered rasters are formed in odd-numbered passes. For example, in pass 10, dots are formed on raster 118 and raster 126, and in pass 11, raster 117, raster 125, and raster 133 are formed. The dots formed on the even raster are arranged at positions shifted in the transport direction with respect to the dots formed on the odd raster.

  The area after the staggered area is returned to the original resolution of 2400 dpi to form a raster.

  Next, with reference to FIG. 5, the process executed by the dot distribution process program 33b executed by the CPU 32 will be described. FIG. 5 is a flowchart showing processing executed by the dot distribution processing program 33b. In this dot distribution process, print data is input assuming that printing is performed at a resolution of 2400 dpi, and conversion is performed so that dots are arranged in a zigzag pattern in an area where the print data is printed at double resolution. is there. Since this process is a process for one sheet of recording paper, it is necessary to perform this process a plurality of times when printing on a plurality of sheets of recording paper.

  First, i, which is a variable indicating the dot position (dot order in the main scanning direction) for forming a raster, is set to 0, and j, which is a variable indicating the order of the raster in the transport direction, is set to 0 (S1). Next, 8 bits are sequentially read from the input print data, and it is determined whether the raster to which the 8-bit data belongs is an area to be printed with double resolution (S2). In this embodiment, which ROM to which raster is to be recorded at double resolution is stored in the ROM 33 in advance, and whether or not the read data is recorded at double resolution based on the storage. Shall be judged.

  When the print data is recorded at normal resolution instead of double resolution (S2: No), the mask applied to the even raster is set to FF in hexadecimal ("0x" shown in the flowchart represents hexadecimal), A mask to be applied to the odd raster is set to 00 in hexadecimal (S3). Therefore, the even rasters are sorted so that dots are formed in any row and the odd rasters are not formed with any dots. In FIG. 3 and FIG. 4, even numbers and odd numbers are reversely assigned to raster numbers.

  On the other hand, when printing data is recorded at double resolution (S2: Yes), the mask applied to the even raster is set to AA in hexadecimal and the mask applied to the odd raster is set to 55 in hexadecimal (S4). Accordingly, in the even raster, dots are formed in even rows and dots are not formed in odd rows, and in odd rasters, dots are not formed in even rows and dots are formed in odd rows.

  When the process of S3 or S4 is completed, the print data is multiplied by the set mask, and the multiplied print data is stored in the image memory 37 (S5). Next, it is determined whether or not the value of i has reached the value to be converted up to the last dot of the raster (S6). If not yet reached (S6: No), i is incremented (S7), Returning to the process of S2 so that the next 8-bit value constituting the raster is read and converted, and when the last dot of the raster has been reached (S6: Yes), the variable j indicating the raster is at the end of the page It is determined whether it is a raster of (S8). If it is not the last raster of the page (S8: No), the variable j is incremented, and the process returns to S2 so as to perform the process for the next raster, and if it is the last raster of the page (S8: Yes). Since all the raster processing for this page has been completed, the dot distribution processing ends.

  As described above, as described in the first embodiment, in the print area where the conveyance skip occurs, the resolution is increased and the dot arrangement is staggered. As a result, even when the conveyance feed skip occurs, the occurrence of banding such as white streaks can be prevented, and high-quality printing can be performed.

  Next, a second embodiment will be described. In the first embodiment, banding is suppressed by forming an area for printing with a normal resolution and an area with a high resolution and dots arranged in a staggered arrangement. At the boundary, since the resolution changes abruptly, there may be a slight straight line whose hue changes in a direction perpendicular to the transport direction. In the second embodiment, the resolution gradually changes to prevent the occurrence of this straight line. That is, in the area (first intermediate area) where the normal area shifts to the high resolution area (second intermediate area), recording is performed so that the resolution gradually increases, and the high resolution area shifts to the normal area. In the region to be performed (third intermediate region), dots are formed such that the resolution gradually decreases. In the region where the resolution is increased, the dot arrangement is a staggered arrangement. This will be described with reference to FIG. 6 and FIG. In the description of the second embodiment, the description of the same parts as those of the first embodiment will be omitted, and only different parts will be described.

  FIGS. 6 and 7 show the path through which each raster is formed and the arrangement of dots corresponding to the raster, as in FIGS. 3 and 4 referred to in the description of the first embodiment. It is. The last row shown in FIG. 6 is a raster 73, which is connected to the raster 74 in the first row shown in FIG.

  As shown in FIG. 6, up to raster 5 is an area where dots are arranged at a normal resolution, and raster 7 to raster 45 are areas where the resolution is gradually increased (first intermediate area). To the raster 66 is a double resolution area (second intermediate area). The raster 67 to raster 105 spanning FIG. 6 and FIG. 7 is an area (third intermediate area) where the resolution is gradually lowered.

  In the first intermediate region and the third intermediate region, the resolution changes by changing the ratio between the high resolution section and the low resolution section. In the first intermediate area, one raster (raster 11, 19) is set to high resolution in the section indicated by (A) from raster 7 to raster 13 and the section indicated by (B) from raster 15 to raster 21. A staggered arrangement is used, and the other rasters have normal resolution. In the section indicated by (c) from the next raster 23 to the raster 29 and the section indicated by (d) from the raster 31 to the raster 37, two rasters (raster 25, 27 and raster 33, 35) are set to high resolution. The section indicated by (e) from the next raster 39 to the raster 45 is in a staggered arrangement, and the three rasters (rasters 39, 41, and 43) have a high resolution and a staggered arrangement. That is, in the first intermediate region, dots are arranged so that the proportion of the section with higher resolution gradually increases as the second intermediate region is approached.

  On the other hand, in the third intermediate area, in the section indicated by (f) from raster 67 to raster 73, the three rasters (rasters 69, 71, 73) have high resolution and a staggered arrangement. Two rasters (raster 77, 79 and raster 85, 87) have high resolution and a staggered arrangement in the section indicated by (G) up to 81 and in the section indicated by (H) from raster 83 to raster 89. In the section indicated by (i) from the raster 91 to the raster 97 and the section indicated by (nu) from the raster 99 to the raster 105, one raster (raster 93, 101) has a high resolution and a staggered arrangement. That is, in the third intermediate region, dots are arranged so that the proportion of the section with higher resolution gradually decreases as the distance from the second intermediate region increases.

  Next, the process of distributing dots as shown in FIGS. 6 and 7 will be described with reference to FIG. FIG. 8 is a flowchart showing the dot distribution process. In this flowchart, the same processing steps as those in the flowchart shown in FIG. 5 are denoted by the same step numbers, and description thereof is omitted.

  In the determination process of S2, if it is determined that the print area is not the double resolution (S2: No), it is determined whether the print area is the first intermediate area or the third intermediate area in which the normal resolution and the double resolution are mixed ( S11). If it is not a mixed area (S11: No), the resolution is normal, so the process proceeds to S3, and a mask for setting a normal dot arrangement is set.

  On the other hand, if it is a mixed area (S11: Yes), it is determined whether the print resolution is normal resolution or double resolution for each raster (S12). For this determination, for example, which raster has the double resolution may be stored in the ROM 33 in advance, and may be determined according to the storage, or may be determined by calculation. The case of determination by calculation will be described later with reference to FIG. It is determined whether or not the determination result is a raster that prints at double resolution. If the raster is not a raster that prints at double resolution (S13: No), the process proceeds to S3, and the raster is printed at double resolution. If there is (S13: Yes), the process proceeds to S4.

  Next, with reference to FIG. 9, a description will be given of a process for determining the resolution of the raster by the calculation which is the process of S12 of the flowchart shown in FIG. FIG. 9 is a flowchart showing processing for determining the resolution of the raster. In this process, the mixed area is divided into N areas in the transport direction, and the i-th raster in the k-th area is set to normal resolution or double resolution. In this setting method, when the resolution is gradually increased, a raster having a high resolution is set at a ratio of (2 to the (k−1) th power) / (2 to the Nth power). For example, when the mixed area is divided into three areas, the first area has 8 rasters with high resolution, and the second area has 8 rasters with 2 rasters with high resolution. Then, 4 rasters per 8 rasters are set to high resolution.

  On the other hand, in the area where the resolution is gradually lowered from the double resolution, when dividing into three areas in the same manner, in the area adjacent to the first double resolution area, 4 rasters are set to a high resolution for 8 rasters, and the next In this area, 2 rasters with 8 rasters have a high resolution, and in an area adjacent to the normal resolution, 1 raster with 8 rasters has a high resolution.

  First, it is determined whether or not the raster to be processed is a region (first intermediate region) where the normal resolution region is shifted to the double resolution (S21). If it is the first intermediate region (S21: Yes), the following equation is calculated,

この演算により求められた値が、０であるか否かを判断する（Ｓ２２）。なお、数式における「％」は、除算を行った商の整数部をとることを示す演算子である。求められた値が０である場合は（Ｓ２２：Ｙｅｓ）、２倍解像度で印刷を行うラスタに設定し（Ｓ２４）、０でない場合は（Ｓ２２：Ｎｏ）、通常解像度で印刷を行うラスタに設定する（Ｓ２５）。

It is determined whether or not the value obtained by this calculation is 0 (S22). Note that “%” in the mathematical expression is an operator indicating that an integer part of a quotient obtained by division is taken. When the obtained value is 0 (S22: Yes), it is set to a raster that prints at double resolution (S24), and when it is not 0 (S22: No), it is set to a raster that prints at normal resolution. (S25).

  In the determination process of S21, when the raster to be processed is not the first intermediate area (S21: No), it is determined to be the third intermediate area, and the following equation is calculated.

この演算により求められた値が、０か否かを判断する（Ｓ２３）。求められた値が０である場合は（Ｓ２３：Ｙｅｓ）、２倍解像度で印刷を行うラスタに設定し（Ｓ２４）、０でない場合は（Ｓ２３：Ｎｏ）、通常解像度で印刷を行うラスタに設定する（Ｓ２５）。

It is determined whether or not the value obtained by this calculation is 0 (S23). When the obtained value is 0 (S23: Yes), it is set to a raster that prints at double resolution (S24), and when it is not 0 (S23: No), it is set to a raster that prints at normal resolution. (S25).

  As described above with respect to the second embodiment, in the second intermediate region where banding occurs, the first intermediate region has a double resolution and a staggered dot arrangement, and transitions from the normal resolution to the double resolution. In addition, by providing a third intermediate area that transitions from the double resolution to the normal resolution, the boundary between the area where the dots are staggered at the double resolution and the area where the dots are normally arranged at the normal resolution is a straight line. Can be prevented from appearing.

  Therefore, even when the carry-feed skip occurs, it is possible to suppress the occurrence of banding, prevent image disturbance due to a change in resolution, and perform high-quality printing.

  Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and various modifications can be easily made without departing from the spirit of the present invention. It can be done.

  For example, in the above embodiment, the processing in the color ink jet printer has been described. However, the processing may be performed in a multi-function peripheral device or a device such as a facsimile machine.

  In the above embodiment, printing is performed on recording paper as the recording medium. However, the recording medium is not limited to paper, and includes cloth, vinyl, and the like.

  In the second embodiment, the process of setting the raster resolution by calculation in the mixed area has been described. However, the present invention is not limited to the above process, and the mixed area is similarly divided into N areas in the transport direction. In the first intermediate area, raster data is distributed at a ratio of k / (N + 1) in the kth area, and in the third intermediate area at a ratio of (N + 1−k) / (N + 1) in the kth area. Raster data may be distributed. For example, when the first intermediate area is divided into seven, the first area is 1 raster per 8 rasters, the second area is 2 rasters per 8 rasters, and the third area is 3 rasters per 8 rasters. Similarly, in the seventh area adjacent to the double resolution, 7 rasters per 8 rasters may be set to double resolution to form a staggered arrangement.

  Similarly, when the third intermediate area is divided into 7 areas, 7 rasters are added to 8 rasters in the first area, 6 rasters are added to 8 rasters in the second area, and 8 rasters are applied in the third area. Similarly, in the seventh area adjacent to the normal resolution, 1 raster per 8 rasters may be double resolution and staggered.

1 is a block diagram illustrating an electrical configuration of a color inkjet printer having an image processing apparatus according to a first embodiment of the present invention. It is a schematic diagram showing the arrangement of dots formed on the recording paper, (a) shows the state recorded in the normal state, (b) shows the state recorded when the transport feed skip occurs Show. It is a figure for demonstrating the distribution method of the dot formed by an interlace system. FIG. 4 is a diagram illustrating a dot distribution method subsequent to FIG. 3. It is a flowchart which shows a dot distribution process. It is a figure for demonstrating the dot distribution method in 2nd Embodiment. FIG. 7 is a diagram for explaining a dot distribution method following FIG. 6. It is a flowchart which shows the dot distribution process in 2nd Embodiment. It is a flowchart which shows the process which sets the resolution of the raster of the mixing area | region in 2nd Embodiment. It is a side view which shows the printer part in a prior art. It is a schematic diagram which shows arrangement | positioning of the dot in a prior art, (a) shows the state recorded in the normal state, (b) shows the state recorded when conveyance feeding skip generate | occur | produced.

Explanation of symbols

1 Color Inkjet Printer 1a Printer Unit (Recording Unit)
32 CPU (control means)
33 ROM
34
RAM
41 LF motor drive circuit (part of transport means)
101 Conveying roller (part of the first conveying member)
102 Pinch roller (part of the first conveying member)
103 Paper discharge roller (part of second conveying member)
104 Spur (part of second transport member)
109 Inkjet head

Claims (8)

A recording means for performing recording by forming a raster composed of a plurality of dots at a predetermined interval in a direction intersecting a conveyance direction for conveying the recording medium;
A first conveying member disposed on the upstream side in the conveying direction of the recording medium with respect to a recording position by the recording unit, and disposed on the downstream side in the conveying direction with the recording unit interposed therebetween than the first conveying member. A conveying means for driving the first conveying member and the second conveying member to convey the recording medium from the upstream side to the downstream side.
A region where recording is performed by the recording unit while transporting the recording medium by the first transport member is defined as a first region, and a region where recording is performed by the recording unit while transporting only by the second transport unit is second. When the predetermined region that is not adjacent to the second region is the first intermediate region and the region sandwiched between the first intermediate region and the second region is the second intermediate region. In the first area recorded before the first intermediate area, the resolution in the recording conveyance direction by the recording means is the first resolution, and in the second intermediate area, the resolution in the conveyance direction is higher than the first resolution. The first intermediate area includes control means for gradually increasing the resolution from the first resolution to the second resolution as the resolution in the transport direction approaches the second intermediate area. Image forming apparatus   In the first intermediate region, the control means gradually changes the resolution by changing a ratio of a section in which recording is performed with the first resolution and a section in which recording is performed with the second resolution in the conveyance direction of the recording medium. The image forming apparatus according to claim 1, wherein the image forming apparatus is made high.   The control means divides one raster into a plurality of areas in the second intermediate area and a section in the first intermediate area where recording is performed at the second resolution, and the divided plurality of areas The image forming apparatus according to claim 2, wherein the adjacent regions are arranged so that adjacent regions are shifted in respective transport directions. A recording means for performing recording by forming a raster composed of a plurality of dots at a predetermined interval in a direction intersecting a conveyance direction for conveying the recording medium;
A first conveying member disposed on the upstream side in the conveying direction of the recording medium with respect to a recording position by the recording unit, and disposed on the downstream side in the conveying direction with the recording unit interposed therebetween than the first conveying member. A conveying means for driving the first conveying member and the second conveying member to convey the recording medium from the upstream side to the downstream side.
An area in which the recording medium is conveyed by the first conveying member is a first area, an area in which the recording medium is conveyed only by the second conveying means is a second area, and the first area is adjacent to the second area. In the first area recorded before the intermediate area when the predetermined area is the intermediate area, the resolution in the recording conveyance direction by the recording means is the first resolution,
In the intermediate area, the resolution in the transport direction is set to a second resolution that is higher than the first resolution, one raster is divided into a plurality of areas, and the divided areas are divided into adjacent areas. An image forming apparatus comprising: a control unit arranged so as to be shifted in each conveyance direction.   5. The image forming apparatus according to claim 1, wherein the control unit sets the resolution in the transport direction in the second region to a resolution lower than the second resolution. 6.   In the second area, when a predetermined area adjacent to the first area is set as the third intermediate area, the resolution in the transport direction is increased from the second resolution as the resolution in the transport direction increases away from the first area. 6. The image forming apparatus according to claim 5, further comprising control means for gradually lowering the resolution to 1.   In the third intermediate area, the control means gradually changes a ratio of a section in which recording is performed at the first resolution and a section in which recording is performed at the second resolution in the transport direction of the recording medium. 7. The image forming apparatus according to claim 6, wherein the resolution is gradually lowered.   In the third intermediate area, the control unit divides one raster into a plurality of areas, and the plurality of divided areas are arranged so that adjacent areas are shifted in respective transport directions. The image forming apparatus according to claim 7.

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